Use Search to find the folder where they (the songs)are stored.
Use My Computer to find and open the folder where the songs should be in a very long list.
If you want to clear the lot........ You can then use EDIT > Select all and Delete. Be careful you delete only songs if you do this.
A safer way is to click on the top of the list and holding down Shift, click far down on the list which should highlight all those between. Delete those, and do the same again with more until they are all gone!